Stone-dressing tool



E. 'r. HOLM STONE DRESSING TOOL Filed June 18, 1925 Patented ()ct. 9,1928;

.UNITED STATES V p v 1,687,093 PATENT JOFFICEQJ mama mean Ham; on m esmn, awn-A o'sto seawar- I .sromi-nnn'ssm'e root.

Application filed June 18, 1925, Serial No. tw st, am in. Nerway J'une 7,- 1924. y j

The present invention .relates to stone dressing tools in which a striking hammer is journalled with play on the outer end of rapidly swinging links, members or arms (for instance Roltsens British Patent No. 183450).

In tools of this sort and particularly of the kind wherein the inner ends of the links are pivotally connected with a rotating hub' or spider, the weak point lies in the connection or journalling between the striking hammer proper and the link. This connection consists of bolt, which, however, is strongly subjected to shocks from the hammer when the same with a high velocity and many times a second strikes the stone. Therefore it has been difficult to construct the bolt with a sutliciently great strength without its dimensions being unproportionably large.

The present invention has for its ob ect to remove this drawback by a special construction of the connection between the striking hammer and the link, whereby the bolt will be practically free from the shock actions. I obtain this result by making the hole in the striking hammer, through which the connecting bolt between hammer and link is passed, in such a manner that the contact between along a line, the radius of curvature of the holebeing all over greater than the radius of.

the bolt.

Further, the hammer is of such dimensions that-when hanging upon the bolt and being in contact with same along one line-it constitutes a physical pendulum, i. e. the distance from one of the lower corners of the hammerif this is triangular-to a perpendicular drawn from the point of suspension to the side of the hammer is equal to the momentof inertia of the hammer divided by the product of the hammer mass with the distance between its point of gravity and the said perpendicular.

The invention is illustrated in the annexed drawing, showing the hammer proper, the bolt of suspension and a portion of the link.

The striking hammer l proper is polygonal,

preferably in well known manner triangular with slightly outwardly curved sides. In the middle it has a hole 2 which generally spoken has a correspondingly polygonal shape, the hole corners being, however, made with a curvature, the radius R of which is all over greater than the radius r of the bolt on the portion 3 carrying the hammer. 4 is the link whic swing i -t di ec n of th arrowfi: Thus it will be seen that the edges of the hole have at anypoint a greater radius of curvature than that of the bolt portion 3.

l/Vhen the hammer is hanging upon the bolt as shown inthe drawing and consequently IS in contact with same only along one line at 0, it constitutes a physical pendulum, if it is so made that I T v a. M wherein L is the distance from the hammer corner .9 to a perpendicular drawn from the point of. suspension 0 upon the hammer side, T is the moment of inertia of the hammer, M 1S its mass and a is the. distance from its point of gravity P to the said perpendicular drawn from 0.

During the operation the link is swinging around with a high velocity in the direction of the arrow, and during this motion the hammer strikes the stone each time with one of its corners Owing to the manner of suspension the shock received by the corner cannot be transferred to the bolt 3. The shock is taken up by the mass of the hammer, and

the hammer will rotate through a certain angle and come at rest upon the bolt in a new position, ready for making a new strike.

Claims r 1. In a stone dressing tool a polygonal striking hammer, having a polygonal hole of substantlally the same shape as the hammer,

loosely journaled to rotate on a connecting bolt on the outer portion of a rapidly swinging member, the radius of the bolt being less than the radius of curvature of the corners of the hole in the hammer through which the bolt is passed, whereby the only contact betweten the hammer and thebolt is a linecontac 2. In a stone dressing tool a polygonal striking hammer, having a polygonal hole of substantially the same shape as the hammer, loosely journaled to rotate on a connecting bolt on the outer portion of a rapidly swinging member, the radius of the bolt being less than the radius of curvature of the corners of the hole in the hammer through which the bolt is passed, whereby the only contact between the hammer andthe bolt is a line con tact, the hammer being supported only at its center of percussion on the bolt'and adapted to swing as a physical pendulum, whereby none of the shock produced by the blows of the hammer is transferred to the supporting bolt.

outer portion of a rapidly swinging member, I

the radius of curvature at the corners of said hole being greater than the radius of the bolt 10 and the curve at any corner of said hole passing through the center-of percussion of the hammer When suspended from said corner, whereby When said hammer is suspended the only contact between said hammer and the bolt is along a line passing through the cen-' ter of percussion of the hammer.

In testimony that I claim the foregolng as my lnventlon, I have signed my'name'.

ERLING THUNE HOLM. V 

